Add emscripten functions and types to the C API

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## **[Unreleased]**
 
+- [#1062](https://github.com/wasmerio/wasmer/pull/1062) Expose some opt-in Emscripten functions to the C API
+- [#1032](https://github.com/wasmerio/wasmer/pull/1032) Change the signature of the Emscripten `abort` function to work with Emscripten 1.38.30
 - [#1060](https://github.com/wasmerio/wasmer/pull/1060) Test the capi with all the backends
 - [#1069](https://github.com/wasmerio/wasmer/pull/1069) Add function `get_memory_and_data` to `Ctx` to help prevent undefined behavior and mutable aliasing. It allows accessing memory while borrowing data mutably for the `Ctx` lifetime. This new function is now being used in `wasmer-wasi`.
 - [#1058](https://github.com/wasmerio/wasmer/pull/1058) Fix minor panic issue when `wasmer::compile_with` called with llvm backend.

Makefile

@@ -114,6 +114,10 @@ capi-llvm:
 	cargo build --manifest-path lib/runtime-c-api/Cargo.toml --release \
 		--no-default-features --features llvm-backend,wasi
 
+capi-emscripten:
+	cargo build --manifest-path lib/runtime-c-api/Cargo.toml --release \
+		--no-default-features --features singlepass-backend,emscripten
+
 # We use cranelift as the default backend for the capi for now
 capi: capi-cranelift
 
@@ -129,7 +133,11 @@ test-capi-llvm: capi-llvm
 	cargo test --manifest-path lib/runtime-c-api/Cargo.toml --release \
 		--no-default-features --features llvm-backend,wasi
 
-test-capi: test-capi-singlepass test-capi-cranelift test-capi-llvm
+test-capi-emscripten: capi-emscripten
+	cargo test --manifest-path lib/runtime-c-api/Cargo.toml --release \
+		--no-default-features --features singlepass-backend,emscripten
+
+test-capi: test-capi-singlepass test-capi-cranelift test-capi-llvm test-capi-emscripten
 
 capi-test: test-capi
 

lib/emscripten/src/lib.rs

@@ -325,6 +325,61 @@ impl<'a> EmscriptenData<'a> {
     }
 }
 
+/// Call the global constructors for C++ and set up the emscripten environment.
+///
+/// Note that this function does not completely set up Emscripten to be called.
+/// before calling this function, please initialize `Ctx::data` with a pointer
+/// to [`EmscriptenData`].
+pub fn set_up_emscripten(instance: &mut Instance) -> CallResult<()> {
+    // ATINIT
+    // (used by C++)
+    if let Ok(_func) = instance.dyn_func("globalCtors") {
+        instance.call("globalCtors", &[])?;
+    }
+
+    if let Ok(_func) = instance.dyn_func("___emscripten_environ_constructor") {
+        instance.call("___emscripten_environ_constructor", &[])?;
+    }
+    Ok(())
+}
+
+/// Call the main function in emscripten, assumes that the emscripten state is
+/// set up.
+///
+/// If you don't want to set it up yourself, consider using [`run_emscripten_instance`].
+pub fn emscripten_call_main(instance: &mut Instance, path: &str, args: &[&str]) -> CallResult<()> {
+    let (func_name, main_func) = match instance.dyn_func("_main") {
+        Ok(func) => Ok(("_main", func)),
+        Err(_e) => match instance.dyn_func("main") {
+            Ok(func) => Ok(("main", func)),
+            Err(e) => Err(e),
+        },
+    }?;
+    let num_params = main_func.signature().params().len();
+    let _result = match num_params {
+        2 => {
+            let mut new_args = vec![path];
+            new_args.extend(args);
+            let (argc, argv) = store_module_arguments(instance.context_mut(), new_args);
+            instance.call(
+                func_name,
+                &[Value::I32(argc as i32), Value::I32(argv as i32)],
+            )?;
+        }
+        0 => {
+            instance.call(func_name, &[])?;
+        }
+        _ => {
+            return Err(CallError::Resolve(ResolveError::ExportWrongType {
+                name: "main".to_string(),
+            }))
+        }
+    };
+
+    Ok(())
+}
+
+/// Top level function to execute emscripten
 pub fn run_emscripten_instance(
     _module: &Module,
     instance: &mut Instance,
@@ -338,15 +393,7 @@ pub fn run_emscripten_instance(
     let data_ptr = &mut data as *mut _ as *mut c_void;
     instance.context_mut().data = data_ptr;
 
-    // ATINIT
-    // (used by C++)
-    if let Ok(_func) = instance.dyn_func("globalCtors") {
-        instance.call("globalCtors", &[])?;
-    }
-
-    if let Ok(_func) = instance.dyn_func("___emscripten_environ_constructor") {
-        instance.call("___emscripten_environ_constructor", &[])?;
-    }
+    set_up_emscripten(instance)?;
 
     // println!("running emscripten instance");
 
@@ -356,33 +403,7 @@ pub fn run_emscripten_instance(
         //let (argc, argv) = store_module_arguments(instance.context_mut(), args);
         instance.call(&ep, &[Value::I32(arg as i32)])?;
     } else {
-        let (func_name, main_func) = match instance.dyn_func("_main") {
-            Ok(func) => Ok(("_main", func)),
-            Err(_e) => match instance.dyn_func("main") {
-                Ok(func) => Ok(("main", func)),
-                Err(e) => Err(e),
-            },
-        }?;
-        let num_params = main_func.signature().params().len();
-        let _result = match num_params {
-            2 => {
-                let mut new_args = vec![path];
-                new_args.extend(args);
-                let (argc, argv) = store_module_arguments(instance.context_mut(), new_args);
-                instance.call(
-                    func_name,
-                    &[Value::I32(argc as i32), Value::I32(argv as i32)],
-                )?;
-            }
-            0 => {
-                instance.call(func_name, &[])?;
-            }
-            _ => {
-                return Err(CallError::Resolve(ResolveError::ExportWrongType {
-                    name: "main".to_string(),
-                }))
-            }
-        };
+        emscripten_call_main(instance, path, &args)?;
     }
 
     // TODO atexit for emscripten

lib/runtime-c-api/Cargo.toml

@@ -32,13 +32,19 @@ path = "../wasi"
 version = "0.11.0"
 optional = true
 
+[dependencies.wasmer-emscripten]
+path = "../emscripten"
+version = "0.11.0"
+optional = true
+
 [features]
 default = ["cranelift-backend", "wasi"]
 debug = ["wasmer-runtime/debug"]
 singlepass-backend = ["wasmer-runtime/singlepass", "wasmer-runtime/default-backend-singlepass"]
 cranelift-backend = ["wasmer-runtime/cranelift", "wasmer-runtime/default-backend-cranelift"]
 llvm-backend = ["wasmer-runtime/llvm", "wasmer-runtime/default-backend-llvm"]
 wasi = ["wasmer-wasi"]
+emscripten = ["wasmer-emscripten"]
 
 [build-dependencies]
 cbindgen = "0.9"

lib/runtime-c-api/build.rs

@@ -12,7 +12,7 @@ fn main() {
     let mut out_wasmer_header_file = PathBuf::from(&out_dir);
     out_wasmer_header_file.push("wasmer");
 
-    const WASMER_PRE_HEADER: &str = r#"
+    let mut pre_header = r#"
 #if !defined(WASMER_H_MACROS)
 #define WASMER_H_MACROS
 
@@ -28,17 +28,27 @@ fn main() {
 #endif
 #endif
 
-#endif // WASMER_H_MACROS
-"#;
+"#
+    .to_string();
+
+    #[cfg(feature = "emscripten")]
+    {
+        pre_header += "#define WASMER_EMSCRIPTEN_ENABLED\n";
+    }
+
+    // close pre header
+    pre_header += "#endif // WASMER_H_MACROS\n";
+
     // Generate the C bindings in the `OUT_DIR`.
     out_wasmer_header_file.set_extension("h");
     Builder::new()
         .with_crate(crate_dir.clone())
         .with_language(Language::C)
         .with_include_guard("WASMER_H")
-        .with_header(WASMER_PRE_HEADER)
+        .with_header(&pre_header)
         .with_define("target_family", "windows", "_WIN32")
         .with_define("target_arch", "x86_64", "ARCH_X86_64")
+        .with_define("feature", "emscripten", "WASMER_EMSCRIPTEN_ENABLED")
         .generate()
         .expect("Unable to generate C bindings")
         .write_to_file(out_wasmer_header_file.as_path());
@@ -49,9 +59,10 @@ fn main() {
         .with_crate(crate_dir)
         .with_language(Language::Cxx)
         .with_include_guard("WASMER_H")
-        .with_header(WASMER_PRE_HEADER)
+        .with_header(&pre_header)
         .with_define("target_family", "windows", "_WIN32")
         .with_define("target_arch", "x86_64", "ARCH_X86_64")
+        .with_define("feature", "emscripten", "WASMER_EMSCRIPTEN_ENABLED")
         .generate()
         .expect("Unable to generate C++ bindings")
         .write_to_file(out_wasmer_header_file.as_path());

lib/runtime-c-api/src/import/emscripten.rs

@@ -0,0 +1,145 @@
+//! Functions and types for dealing with Emscripten imports
+
+use super::*;
+use crate::{get_slice_checked, instance::wasmer_instance_t, module::wasmer_module_t};
+
+use std::ptr;
+use wasmer_emscripten::{EmscriptenData, EmscriptenGlobals};
+use wasmer_runtime::{Instance, Module};
+
+/// Type used to construct an import_object_t with Emscripten imports.
+#[repr(C)]
+pub struct wasmer_emscripten_globals_t;
+
+/// Create a `wasmer_emscripten_globals_t` from a Wasm module.
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_emscripten_get_globals(
+    module: *const wasmer_module_t,
+) -> *mut wasmer_emscripten_globals_t {
+    if module.is_null() {
+        return ptr::null_mut();
+    }
+    let module = &*(module as *const Module);
+    match EmscriptenGlobals::new(module) {
+        Ok(globals) => Box::into_raw(Box::new(globals)) as *mut wasmer_emscripten_globals_t,
+        Err(msg) => {
+            update_last_error(CApiError { msg });
+            return ptr::null_mut();
+        }
+    }
+}
+
+/// Destroy `wasmer_emscrpten_globals_t` created by
+/// `wasmer_emscripten_get_emscripten_globals`.
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_emscripten_destroy_globals(
+    globals: *mut wasmer_emscripten_globals_t,
+) {
+    if globals.is_null() {
+        return;
+    }
+    let _ = Box::from_raw(globals);
+}
+
+/// Execute global constructors (required if the module is compiled from C++)
+/// and sets up the internal environment.
+///
+/// This function sets the data pointer in the same way that
+/// [`wasmer_instance_context_data_set`] does.
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_emscripten_set_up(
+    instance: *mut wasmer_instance_t,
+    globals: *mut wasmer_emscripten_globals_t,
+) -> wasmer_result_t {
+    if globals.is_null() || instance.is_null() {
+        return wasmer_result_t::WASMER_ERROR;
+    }
+    let instance = &mut *(instance as *mut Instance);
+    let globals = &*(globals as *mut EmscriptenGlobals);
+    let em_data = Box::into_raw(Box::new(EmscriptenData::new(
+        instance,
+        &globals.data,
+        Default::default(),
+    ))) as *mut c_void;
+    instance.context_mut().data = em_data;
+
+    match wasmer_emscripten::set_up_emscripten(instance) {
+        Ok(_) => wasmer_result_t::WASMER_OK,
+        Err(e) => {
+            update_last_error(e);
+            wasmer_result_t::WASMER_ERROR
+        }
+    }
+}
+
+/// Convenience function for setting up arguments and calling the Emscripten
+/// main function.
+///
+/// WARNING:
+///
+/// Do not call this function on untrusted code when operating without
+/// additional sandboxing in place.
+/// Emscripten has access to many host system calls and therefore may do very
+/// bad things.
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_emscripten_call_main(
+    instance: *mut wasmer_instance_t,
+    args: *const wasmer_byte_array,
+    args_len: c_uint,
+) -> wasmer_result_t {
+    if instance.is_null() || args.is_null() {
+        return wasmer_result_t::WASMER_ERROR;
+    }
+    let instance = &mut *(instance as *mut Instance);
+
+    let arg_list = get_slice_checked(args, args_len as usize);
+    let arg_process_result: Result<Vec<&str>, _> =
+        arg_list.iter().map(|arg| arg.as_str()).collect();
+    let arg_vec = match arg_process_result.as_ref() {
+        Ok(arg_vec) => arg_vec,
+        Err(err) => {
+            update_last_error(*err);
+            return wasmer_result_t::WASMER_ERROR;
+        }
+    };
+
+    let prog_name = if let Some(prog_name) = arg_vec.first() {
+        prog_name
+    } else {
+        update_last_error(CApiError {
+            msg: "First argument (program name) is required to execute Emscripten's main function"
+                .to_string(),
+        });
+        return wasmer_result_t::WASMER_ERROR;
+    };
+
+    match wasmer_emscripten::emscripten_call_main(instance, prog_name, &arg_vec[1..]) {
+        Ok(_) => wasmer_result_t::WASMER_OK,
+        Err(e) => {
+            update_last_error(e);
+            wasmer_result_t::WASMER_ERROR
+        }
+    }
+}
+
+/// Create a `wasmer_import_object_t` with Emscripten imports, use
+/// `wasmer_emscripten_get_emscripten_globals` to get a
+/// `wasmer_emscripten_globals_t` from a `wasmer_module_t`.
+///
+/// WARNING:
+///1
+/// This `import_object_t` contains thin-wrappers around host system calls.
+/// Do not use this to execute untrusted code without additional sandboxing.
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_emscripten_generate_import_object(
+    globals: *mut wasmer_emscripten_globals_t,
+) -> *mut wasmer_import_object_t {
+    if globals.is_null() {
+        return ptr::null_mut();
+    }
+    // TODO: figure out if we should be using UnsafeCell here or something
+    let g = &mut *(globals as *mut EmscriptenGlobals);
+    let import_object = Box::new(wasmer_emscripten::generate_emscripten_env(g));
+
+    Box::into_raw(import_object) as *mut wasmer_import_object_t
+}